[PATCH v4 1/2] rcu: Eliminate rcu_state.nocb_is_setup

From: Zhen Lei
Date: Tue Aug 16 2022 - 21:43:40 EST


'rcu_state.nocb_is_setup' is initialized to true only if 'rcu_nocb_mask'
successfully allocates memory. So it can be replaced by
'cpumask_available(rcu_nocb_mask)'. More importantly, the latter is more
intuitive, and it has been used in several places.

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
kernel/rcu/tree.h | 1 -
kernel/rcu/tree_nocb.h | 8 +++-----
2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index d4a97e40ea9c3e2..06f659c63d2d192 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -375,7 +375,6 @@ struct rcu_state {
arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
/* Synchronize offline with */
/* GP pre-initialization. */
- int nocb_is_setup; /* nocb is setup from boot */
};

/* Values for rcu_state structure's gp_flags field. */
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 0a5f0ef41484518..ff763e7dc53551f 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -69,7 +69,6 @@ static int __init rcu_nocb_setup(char *str)
cpumask_setall(rcu_nocb_mask);
}
}
- rcu_state.nocb_is_setup = true;
return 1;
}
__setup("rcu_nocbs", rcu_nocb_setup);
@@ -1215,7 +1214,7 @@ void __init rcu_init_nohz(void)
struct rcu_data *rdp;

#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL)
- if (!rcu_state.nocb_is_setup) {
+ if (!cpumask_available(rcu_nocb_mask)) {
need_rcu_nocb_mask = true;
offload_all = true;
}
@@ -1235,10 +1234,9 @@ void __init rcu_init_nohz(void)
return;
}
}
- rcu_state.nocb_is_setup = true;
}

- if (!rcu_state.nocb_is_setup)
+ if (!cpumask_available(rcu_nocb_mask))
return;

#if defined(CONFIG_NO_HZ_FULL)
@@ -1299,7 +1297,7 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu)
struct task_struct *t;
struct sched_param sp;

- if (!rcu_scheduler_fully_active || !rcu_state.nocb_is_setup)
+ if (!rcu_scheduler_fully_active || !cpumask_available(rcu_nocb_mask))
return;

/* If there already is an rcuo kthread, then nothing to do. */
--
2.25.1